Yes, you don't need to sign up to set up a profile. You just need to authenticate ; a way to prove that you really own a given account on FriendFeed or Twitter. Don't even worry about your passwords, they're simply not recorded on SocialWhois.
So, go ahead, choose what to use: FriendFeed or Twitter
P.S. Promise, I'm trying hard to integrate OpenID too! :) — directeur.